The three flumes run north-south. Lower, middle and upper flume, along with Mike's trail are in the Highlands residential area. The track illustrated proceeds south along the lower flume, then connects to the upper flume, going north. Eventually it connects with the middle flume coming back around, then to Mike's trail and back down to the Lower Flume to complete the loop. Other routes can be taken.
All singletrack in the trees. (It's a wonder my GPSr actually worked)
To get more detail there are a few maps of the route in the 2006 Bike Guide and the Town of Breck trail map.
Drive to Breckenridge via hwy 9. Parking lot is just west of Hwy 9 on Valley Brook Rd. Ride across Hwy 9, up Highlands Drive about a 100 yds and look for the lower Flume trail sign on both sides of the street.
http://www.singletracks.com/item.php?c=1&i=1812